Composite parts having complex shapes may be formed using vacuum bags comprised of pleated nylon film which may be configured to conform to the shape of the preform. The preform may be preimpregnated (prepreg) or a dry material with resin infused during consolidation. Vacuum is drawn on the vacuum bag in part to debulk the preform. These complex shapes typically include highly contoured or compound contoured surfaces or those with integral shaped details such as without limitation stringers or frames. Current approaches to fabricating composite parts with complex shapes may suffer from several limitations. For example, installing a pleated nylon vacuum bag over a preform may be extremely labor intensive, requiring highly skilled technicians to apply the intricate pleating patterns necessary to avoid bridging of a bag. Bridging may result in a localized reduced vacuum, which may result in resin pooling. In addition, the thin nylon bags may be susceptible to puncture-related leaks, which may occur during nylon bag installation. The nylon bag pleats may pinch off and render leaks more difficult to detect. When a leak is pinched off, the flow of air through the leak is restricted, making a leak harder to identify in a leak check and harder to locate once a leak is known to exist.
One attempt to avoid the leak susceptibility and labor intensive nature of pleated nylon bag installation in the fabrication of composite parts involves the dipping of a metal mandrel into latex, followed by oven curing of the latex on the mandrel. The latex bags thus formed using this approach may also suffer from several limitations. More specifically, the latex used in forming vacuum bags in this manner may shrink nonuniformly as it cures depending upon physical constraints inherent in the complex shape of the part. This limits the extent of conformance of the thus formed latex bag to the outer surface of the metal mandrel representing the composite part to be fabricated. Silicone bags have also been used, but they may be expensive to manufacture and present a clean room contamination problem. Accordingly, there is a need for a vacuum bag which overcomes the aforementioned limitations.